250 
PALAEONTOLOGY OF NEW YORK. 
mm.; the approximate length is 70 mm. and 88 mm., respectively. Another 
specimen has a length of 77 mm., and a height of 90 mm. A larger speci¬ 
men has a length of 90 mm., and a height of 100 mm. 
The specimens of this species occur in the softer shales of the Hamilton 
group, and it is possible that long maceration has had some influence in oblite¬ 
rating the radii; but L. macroptera, with its more convex form, and marked by 
its characteristic radii, occurs in the same localities. Although not entirely 
satisfied in regard to its specific distinction, it may be convenient to separate 
this at least as a varietal form. 
Formation and localities. In the Hamilton group, at Hamilton, Madison county, 
at Delphi, Onondaga county; and on the shore of Cayuga lake, N. Y. 
Limoptera curvata. 
PLATE XXVIII, FIGS. 1-3. 
IAmoptera curvata, Hall. Prelim. Notice, Lam. Shells, etc., part 2, p. 18. Dec., 1869. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 28, figs. 1-3. Jan., 1883. 
Shell large, sub-rhomboid-ovate in outline; body broadly ovate, arcuate, 
expanded on the antero-basal margin. 
Yalves very unequal. Left valve very gibbous in the middle and umbonal 
region. Right valve depressed-convex below, becoming somewhat gibbous 
on the umbo. Left valve, with the beak, very prominent and incurved; 
beak of right valve rising but little above the hinge-line. 
Test thick, marked by strong rounded radii with intermediate finer lines 
which become obsolete on the lower part of the valve. The radii are crossed 
by fine, closely arranged striae of growth, which at intervals are crowded and 
lamellose, especially toward the margin of the valve. 
The internal cast shows the anterior muscular impression situated at the 
extremity of the rostral cavity, from which the pallial line, marked by a 
row of strong pustules, extends nearly parallel to the anterior margin for 
more than one-third the length of the valve; thence broadly curving, it 
extends below the middle of the valve, and recurves into a large sub-circular 
